Current technology now makes it possible to transmit and receive voice signals, facsimile signals, and/or data signals over networks such as the Internet. In one example, to create a typical communications link using a network, an individual makes a local telephone call from a first telephone to a first network gateway over a local telecommunications network. The individual informs the gateway of the desired telephone number to be contacted. The first network gateway, in turn, identifies a second network gateway on the network that can contact the desired number. The first gateway then contacts the second network gateway via the network such as the Internet. The second network then contacts a second telephone via the local telecommunications network. This approach may be employed to conduct long distance calls at local telephone rates.
The network gateways typically include logical circuitry and/or software/firmware executed by a processor circuit to provide for gateway operation in the voice, facsimile, and data communications modes. Also, the network gateways may include logical circuitry and/or software/firmware executed by a processor circuit to switch the mode of operation between the voice, facsimile, and data communications modes.
For example, when a facsimile is transmitted from the first and second gateways, initially a telephone call is established between first and second facsimile machines and their respective gateways. After the telephone link is established, facsimile machines typically conduct startup negotiations using various tones, etc., to facilitate the transfer of a document. When the facsimile machines attempt to begin the startup negotiations, the respective gateways detect the tones transmitted and switch to a facsimile operating mode to facilitate the transfer of a document. The gateways then conduct the startup negotiations with their respective facsimile machines.
While this technique of establishing facsimile communication works most of the time, it is susceptible to error due to the so called “secretary problem”. Assume, for example, that a voice call is established in the manner described above from a telephone in an office environment. Also assume that a facsimile is physically located within hearing distance of the individual making the telephone call. During the voice conversation, assume that the facsimile is employed to transmit a facsimile across a separate telephone line or other channel. During the course of the startup negotiations with a remote facsimile, the facsimile transmits the various tones used in the startup negotiations of the facsimile transfer. These tones may often be heard as audible tones in the office environment.
If the telephone receiver that is currently in use for the telephone conversation is close enough to the facsimile, it inevitably picks up the audible tones that are transmitted by the facsimile. These tones are then relayed to the gateways that are currently employed to facilitate the voice conversation. Unfortunately, these facsimile tones can mislead the gateways. Specifically, upon detecting these tones, the gateways are led to believe that the current voice call is to be switched into a facsimile call and they switch to facsimile operating mode accordingly. When this occurs, the telephone conversation is disrupted to the annoyance of the individuals involved in the discussion.